(i)[4]
By writing the length of $BD$ in terms of $\theta$ in both triangles $ABD$ and $DBC$, prove that $20\sin^2\theta = 9\cos\theta$.
(ii)[3]
Hence, with all required working shown, calculate $\theta$.
Mathematics 9709 · AS & A Level · Trigonometry
Trigonometry — practice question
The diagram depicts triangle $ABC$, where $BC = 20\text{ cm}$ and angle $ABC = 90^\circ$. The perpendicular drawn from $B$ to $AC$ meets $AC$ at $D$, with $AD = 9\text{ cm}$. The angle $BCA$ is $\theta$.